Rotary member support structure, transport device, charging device, and image forming apparatus

ABSTRACT

A rotary member support structure includes: a rotary member including a shaft; a bearing that rotatably supports the shaft of the rotary member; a pressing member that presses the bearing in one direction; and a support that supports the bearing such that the bearing is movable in a pressing direction of the pressing member. When the rotary member is not rotating, the bearing and the pressing member are in contact with each other such that the bearing is rotatable about the shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2017-233292 filed Dec. 5, 2017.

BACKGROUND Technical Field

The present invention relates to a rotary member support structure, to atransport device, to a charging device, and to an image formingapparatus.

SUMMARY

According to an aspect of the invention, there is provided a rotarymember support structure including: a rotary member including a shaft; abearing that rotatably supports the shaft of the rotary member; apressing member that presses the bearing in one direction; and a supportthat supports the bearing such that the bearing is movable in a pressingdirection of the pressing member. When the rotary member is notrotating, the bearing and the pressing member are in contact with eachother such that the bearing is rotatable about the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a schematic diagram showing the structure of an image formingapparatus;

FIG. 2 is an enlarged schematic diagram showing an output transport pathnear a fixing device in the image forming apparatus in FIG. 1;

FIG. 3 is a partial schematic cross sectional view showing the structureof a pair of first output rollers in the output transport path in FIG. 2(the structure includes support structures);

FIG. 4A is a schematic diagram showing a support structure for a drivenroller in the pair of output rollers in FIG. 3 in exemplary embodiment1;

FIG. 4B is a schematic cross-sectional view taken along line IVB-IVB inFIG. 4A;

FIG. 5A is an enlarged schematic diagram showing the support structurefor the driven roller in FIG. 4A;

FIG. 5B is a schematic diagram showing a contact state of a protrusionin the support structure in FIG. 5A;

FIG. 6A is a schematic diagram showing a state when the driven roller inthe support structure in FIG. 5A is not rotating;

FIG. 6B is a schematic diagram showing a state during rotation of thedriven roller in the support structure in FIG. 6A;

FIG. 7A is an exploded perspective view showing the structure of apressing member including the protrusion in the support structure inFIG. 5A;

FIG. 7B is a schematic cross-sectional view showing the pressing memberin FIG. 7A;

FIG. 8A is an enlarged schematic diagram showing a support structure forthe driven roller in exemplary embodiment 2;

FIG. 8B is a schematic diagram showing a contact state of a protrusionin the support structure;

FIG. 9A is a schematic diagram showing a state when the driven roller inthe support structure in FIG. 8A is not rotating;

FIG. 9B is a schematic diagram showing a state during rotation of thedriven roller in the support structure in FIG. 9A;

FIG. 10A is a schematic perspective view showing the structure of theprotrusion in the support structure in FIG. 8A;

FIG. 10B is a schematic perspective view showing another example of thestructure of the protrusion in the support structure;

FIG. 11A is an enlarged schematic diagram showing a support structurefor the driven roller in exemplary embodiment 3;

FIG. 11B is a schematic diagram showing a contact state of a protrusionin the support structure;

FIG. 12A is a schematic diagram showing a state when the driven rollerin the support structure in FIG. 11A is not rotating;

FIG. 12B is a schematic diagram showing a state during rotation of thedriven roller in the support structure in FIG. 12A;

FIG. 13 is an enlarged schematic diagram showing a support structure fora charging roller in exemplary embodiment 4;

FIG. 14A is a schematic diagram showing a state when the charging rollerin the support structure in FIG. 13 is not rotating;

FIG. 14B is a schematic diagram showing a state during rotation of thecharging roller in the support structure in FIG. 14A;

FIG. 15A is an enlarged schematic diagram showing a comparative supportstructure for the driven roller;

FIG. 15B is a schematic diagram showing a contact state between apressing member and a bearing in the support structure;

FIG. 16A is a schematic diagram showing a state when the driven rollerin the support structure in FIG. 15A is not rotating; and

FIG. 16B is a schematic diagram showing a state during rotation of thedriven roller in the support structure in FIG. 16A.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will next be describedwith reference to the drawings.

EXEMPLARY EMBODIMENT 1

FIGS. 1 and 2 show exemplary embodiment 1 of the invention. FIG. 1 showsthe structure of an image forming apparatus 1 according to exemplaryembodiment 1. FIG. 2 is an enlarged illustration of an output transportpath in the image forming apparatus 1 in FIG. 1.

<General Structure of Image Forming Apparatus>

In the image forming apparatus 1, an image based on the informationabout an image including letters, photographs, diagrams, etc. is formedusing a developer on a recording paper sheet 9 that is an example of atransportation object or a recording medium.

As shown in FIG. 1, the image forming apparatus 1 includes: a housing 10serving as an apparatus body; an image forming unit 2 that forms a tonerimage using a toner serving as the developer by, for example,electrophotography and transfers the toner image onto a recording papersheet 9; a paper feeder 3 that holds a prescribed number of recordingpaper sheets 9 and feeds a recording paper sheet 9 to a transferposition of the image forming unit 2; and a fixing device 4 that fixesthe toner image transferred onto the recording paper sheet 9. The imageforming unit 2, the paper feeder 3, and the fixing device 4 are disposedinside the housing 10.

The housing 10 is composed of various members such as structural membersand exterior materials. An output tray 11 for placing ejected recordingpaper sheets 9 with images formed thereon is provided in an upperportion of the housing 10. The output tray 11 is formed as a collectingsurface having an inclined surface disposed below a paper outlet 12 ofthe housing 10 and is configured to collect recording paper sheets 9ejected from the paper outlet 12.

The image forming unit 2 includes a photoreceptor drum 21 that is adriving drum and rotates in a direction indicated by arrow A and furtherincludes a charging device 22, an exposure device 23, a developingdevice 24, a transfer device 25, and a cleaning device 26 that aredisposed in this order around the photoreceptor drum 21.

The charging device 22 is, for example, a contact charging device thatelectrically charges the circumferential surface (the outercircumferential surface serving as an image-forming region) of thephotoreceptor drum 21 to a prescribed potential with a prescribedpolarity. The exposure device 23 irradiates the circumferential surfaceof the charged photoreceptor drum 21 with light (indicated by a chaindouble-dashed arrow) in response to image information (signals) inputtedin various forms to the image forming apparatus 1 to thereby form anelectrostatic latent image. The developing device 24 supplies a chargedtoner used as a developer to develop the electrostatic latent image onthe photoreceptor drum 21, and a toner image is thereby formed. Thetransfer device 25 is, for example, a contact transfer device thatelectrostatically transfers the toner image on the photoreceptor drum 21onto a recording paper sheet 9. The cleaning device 26 cleans thephotoreceptor drum 21 by removing undesired substances such as the tonerremaining on the circumferential surface of the photoreceptor drum 21.

The paper feeder 3 includes: a paper tray 31 that holds plural recordingpaper sheets 9 having a prescribed size and a prescribed type and usedfor image formation, the recording paper sheets 9 being stacked on asheet stacking plate 32; and a delivery unit 33 that delivers therecording paper sheets 9 held in the paper tray 31 one by one.

The paper tray 31 is attached to the housing 10 such that the paper tray31 can be pulled out of the housing 10, and plural paper trays 31 may beprovided depending on use conditions. The recording paper sheets 9 usedare, for example, recording mediums cut into a prescribed size such asplain paper sheets, coated paper sheets, or thick paper sheets.

The fixing device 4 includes a housing 40 having an inlet for arecording paper sheet 9 and a paper outlet and further includes aheating rotary body 41 and a pressurizing rotary body 42 that aredisposed inside the housing 40 and rotate while in contact with eachother.

As shown in FIGS. 1 and 2 etc., the heating rotary body 41 is a drivingrotary body and rotates in a direction indicated by an arrow. Theheating rotary body 41 is a fixing member for heating and is in a rollerform or a belt-pad form, and the circumferential surface of the heatingrotary body 41 is heated to a prescribed temperature by a heater 43. Thepressurizing rotary body 42 is a fixing member for pressurization thatis in a roller form or a belt-pad form and is disposed so as to bealigned substantially along the axial direction of the heating rotarybody 41. The pressurizing rotary body 42 is in contact with the heatingrotary body 41 at a prescribed pressure and is rotated by the heatingrotary body 41. In the fixing device 4, the contact portion between theheating rotary body 41 and the pressurizing rotary body 42 serves as afixing treatment section FN through which a recording paper sheet 9 witha non-fixed toner image transferred thereon passes to thereby subject itto prescribed fixing treatment (heating, pressurization, etc.).

<Structure of Transport Path>

In the image forming apparatus 1, as shown by a chain double-dashed linein FIG. 1, a transport path Rt for transportation of a recording papersheet 9 is provided in the housing 10. The transport path Rt includes asupply transport path Rt1, a relay transport path Rt2, and an output thetransport path Rt3.

As shown in FIG. 1, the supply transport path Rt1 connects the deliveryunit 33 of the paper feeder 3 to the transfer position (a portion of thephotoreceptor drum 21 that faces the transfer device 25) of the imageforming unit 2. The supply transport path Rt1 is composed of a pair oftransport rollers 34 and unillustrated plural transport guide members.

The pair of transport rollers 34 are composed of so-called resistrollers. The resist rollers in a non-rotating state have the function ofcorrecting the inclination of a transported recording paper sheet 9. Theresist rollers start rotating at the timing of transfer, and therotating resist rollers have the function of feeding a recording papersheet 9 to the transfer position.

As shown in FIG. 1, the relay transport path Rt2 connects the transferposition of the image forming unit 2 to the fixing treatment section ofthe fixing device 4. The relay transport path Rt2 is composed of aprescribed guide member 35.

As shown in FIGS. 1 and 2 etc., the output transport path Rt3 connectsthe fixing treatment section FN of the fixing device 4 to the paperoutlet 12. The output transport path Rt3 is composed of a pair of firstoutput rollers 36, a pair of second output rollers 37, plural outputguiding members 38 and 39, etc.

The pair of first output rollers 36 is disposed on the paper outlet sideof the housing 40 of the fixing device 4 and includes a driving roller361 and a driven roller 362 that is pressed against the driving roller361 and driven to rotate by the driving roller 361. The pair of secondoutput rollers 37 is disposed at the paper outlet 12 and includes adriving roller 372 and a driven roller 371 that is in contact with thedriving roller 372 and is driven to rotate by the driving roller 372. Asupport structure for the pair of first output rollers 36 will bedescribed later.

The output guiding members 38 are a pair of members 38 a and 38 b thatface each other so as to form a transport space through which arecording paper sheet 9 subjected to fixation is guided to the pair offirst output rollers 36. The output guiding members 39 are a pair ofmembers 39 a and 39 b that face each other so as to form a transportspace through which a recording paper sheet 9 discharged from the pairof first output rollers 36 is guided to the pair of second outputrollers 37.

<Image Forming Operation by Image Forming Apparatus>

In the image forming apparatus 1, an image is formed as described below.An image forming operation for forming an image on one side of arecording paper sheet 9 will be described.

First, when an unillustrated controller in the image forming apparatus 1receives an image formation request, the image forming unit 2, the paperfeeder 3, and the fixing device 4 are actuated.

Then, in the image forming unit 2, the photoreceptor drum 21 startsrotating. The charging device 22 charges the circumferential surface ofthe photoreceptor drum 21 to a predetermined potential with apredetermined polarity (a negative polarity in this embodiment), andthen the exposure device 23 exposes the charged circumferential surfaceof the photoreceptor drum 21 to light according to image information tothereby form an electrostatic latent image having a prescribed pattern.Next, the developing device 24 supplies a toner serving as a developerand charged to a prescribed polarity (a negative polarity in thisembodiment) to the electrostatic latent image formed on thecircumferential surface of the photoreceptor drum 21 to develop theelectrostatic latent image, and the electrostatic latent image isthereby converted to a visible toner image.

Next, in the image forming unit 2, the rotating photoreceptor drum 21transfers the toner image to the transfer position facing the transferdevice 25. The delivery unit 33 of the paper feeder 3 feeds a recordingpaper sheet 9 to the supply transport path Rt1 according to transfertiming, and the pair of resist rollers 34 in the supply transport pathRt1 delivers the recording paper sheet 9 to the transfer position. Then,in the image forming unit 2, the transfer device 25 transfers the tonerimage on the photoreceptor drum 21 onto one side of the recording papersheet 9 through electrostatic action at the transfer position. In theimage forming unit 2, after the image transfer, the cleaning device 26cleans the circumferential surface of the photoreceptor drum 21 andother portions to prepare for the next image forming process.

Next, in the image forming unit 2, the rotational force of the rotatingphotoreceptor drum 21 causes the recording paper sheet 9 with the tonerimage transferred thereon to be delivered to the relay transport pathRt2 and transported to the fixing device 4. In the fixing device 4, therecording paper sheet 9 is introduced into the fixing treatment sectionFN between the heating rotary body 41 and the pressurizing rotary body42 driven to rotate by the heating rotary body 41. When the recordingpaper sheet 9 passes through the fixing treatment section FN, the tonerimage on the recording paper sheet 9 is heated and fused under pressureand is thereby fixed to the recording paper sheet 9.

Finally, the recording paper sheet 9 subjected to fixation istransported through the output transport path Rt3 to the paper outlet 12of the housing 10 and then ejected and placed in the output tray 11.

In this case, as shown in FIGS. 1 and 2, the recording paper sheet 9subjected to fixation is guided by the output guiding members 38 and theoutput guiding members 39 in the output transport path Rt3, held betweenthe pair of first output rollers 36 and then between the pair of secondoutput rollers 37, and transported by the transportation force of therollers.

A single-color toner image is thereby formed on one side of therecording paper sheet 9, and the single-side image formation operationis completed. When an instruction to perform the image forming operationplural times is issued, the above series of operations is repeated theplural times.

<Support Structure for Pair of First Output Rollers and Transport DeviceUsing the Same>

In the image forming apparatus 1, a support structure shown in FIGS. 3to 6B etc. is used as the support structure supporting the pair of firstoutput rollers 36 disposed in the output transport path Rt3.

First, as shown in FIG. 3 etc., in the pair of first output rollers 36,a rotary member 5A including a rotating shaft 51 serving as a shaft androller bodies 53 disposed on the outer circumferential surface of therotating shaft 51 is used as the driving roller 361. The driving roller361 in exemplary embodiment 1 is a roller having a structure includingthe plural roller bodies 53 disposed on the rotating shaft 51 atprescribed intervals.

As shown in FIG. 3 etc., in the pair of first output rollers 36, arotary member 5B including a rotating shaft 52 serving as a shaft and aroller body 54 disposed on the outer circumferential surface of therotating shaft 52 is used as the driven roller 362. The driven roller362 in exemplary embodiment 1 is a roller having a structure includingone roller body 54 disposed on the rotating shaft 52.

The pair of first output rollers 36 has a structure in which therotating shafts 51 and 52 are rotatably supported by prescribed supportmembers 70 through bearings 55 and 56, respectively, such that theroller bodies 53 and 54 of the driving roller 361 and the driven roller362, respectively, forming the rotary members 5A and 5B rotate while incontact with each other.

The support members 70 are plate members such as synthetic resin platesor metallic plates fixed to prescribed positions.

As shown in FIGS. 1 to 3 etc., the pair of first output rollers 36 formsa transport device 7 that transports a recording paper sheet 9, which isan example of a transportation object. Specifically, the recording papersheet 9 is transported while sandwiched between the driving roller 361and the driven roller 362 driven to rotate by the driving roller 361.

As shown in FIG. 3, the driving roller 361 is driven to rotate in aprescribed direction by rotating power transmitted to the rotating shaft51 from a rotation driving device 77. The rotating power is transmittedfrom the rotation driving device 77 to the driving roller 361 (to itsrotating shaft 51) using an unillustrated rotation transmittingmechanism such as a gear train.

In the driving roller 361 in the above support structure, the bearings55 rotatably supporting the rotating shaft 51 are fixed to respectivestationary attachment members 71 disposed in the support members 70, andthe driving roller 361 is thereby attached to the support members 70.

The stationary attachment members 71 include, for example, holes orrecesses into which the bearings 55 are partially fitted and memberswhich fix the bearings 55. The bearings 55 are, for example, slidingbearings.

As shown in FIGS. 3 to 5B etc., in the driven roller 362 in the abovesupport structure, the bearings 56 rotatably supporting the rotatingshaft 52 are attached to movable attachment members 72 disposed in thesupport members 70 so as to be movable by a given distance toward thedriving roller 361 as shown by double-pointed arrows E1-E2.

Each of the movable attachment members 72 includes a support 73 thatsupports a corresponding bearing 5 for the driven roller 362 movablywith respect to the rotating shaft 51 of the driving roller 361. Thesupports 73 are attached and fixed to the respective support members 70.The bearings 56 are, for example, sliding bearings. The supports 73 maybe formed as portions of the support members 70 and integratedtherewith.

In the driven roller 362, the bearings 56 supporting the rotating shaft52 are supported by the movable attachment members 72 so as to bepressed by respective pressing members 57 in a direction E1 directedtoward the rotating shaft 51 of the driving roller 361.

As described above, in the pair of first output rollers 36, the drivingroller 361 (the rotary member 5A) is rotatably supported by the supportmembers 70 (their stationary attachment members 71) while the positionof the driving roller 361 is fixed. The driven roller 362 (the rotarymember 5B) is rotatably supported by the supports 73 (the movableattachment members 72) of the support members 70 so as to be movabletoward the driving roller 361 and is also supported by the pressingmembers 57 through the bearings 56 so as to be pressed in the directionE1 directed toward the rotating shaft 51 of the driving roller 361.

In particular, as shown in FIGS. 3, 4A, and 4C, in the pair of firstoutput rollers 36, the driven roller 362 (the rotary member 5B) employsa support structure 6 including: the bearings 56 that rotatably supportthe rotating shaft 52; the pressing members 57 that press the respectivebearings 56 in the direction E1 directed toward the rotating shaft 51 ofthe driving roller 361; and the supports 73 that support the respectivebearings 56 so as to be movable in the direction E1 in which thebearings 56 are pressed by the pressing members 57.

As shown in FIGS. 4A and 4B, each of the bearings 56 in the supportstructure 6 includes a plate-shaped body 56 a having a substantiallyrectangular side portion. Each body 56 a includes: a bearing hole 56 blocated at substantially the center and passing through the body 56 a; astep portion 56 c that is disposed in an upper outer portion of the body56 a and extends in the moving direction E1-E2; and a pressure receivingportion 56 d that receives the pressure of a corresponding pressingmember 57 on one side.

As shown in FIGS. 4A and 4B, each support 73 in the support structure 6includes a body 74 having a holding portion 74 a that accommodates acorresponding bearing 56 such that upper and lower portions of thebearing 56 are held so as to be movable in the direction E1-E2. The body74 includes: a lower guiding portion 74 b that holds and guides thelower side surface of the bearing 56 when it moves; an upper guidingportion 74 c that holds and guides the upper side surface (the stepportion 56 c) of the bearing 56 when it moves; and an abutting portion74 d against which part of the pressing member 57 abuts to fix thepressing member 57.

As shown in FIGS. 4A and 4B, each of the pressing members 57 in thesupport structure 6 is composed of a member that can elastically press acorresponding bearing 56 in the direction E1 directed toward therotating shaft 51 of the driving roller 361. Each of the pressingmembers 57 in exemplary embodiment 1 includes a coil spring.

Each of the coil springs of the pressing members 57 is disposed betweenthe pressure receiving portion 56 d of a corresponding bearing 56 andthe abutting portion 74 d of a corresponding support 73 and is used suchthat the bearing 56 is pressed by prescribed pressing force F toward therotation center (02) of the rotating shaft 52 of the driven roller 362.

As shown in FIG. 4A, in the abutting portion 74 d of the support 73 inexemplary embodiment 1, a protrusion holding portion 74 e that holds oneend of the coil spring used as the pressing member 57 is provided. Theprotrusion holding portion 74 e is fitted into an internal space at theone end of the coil, and the coil spring is thereby held. Since the oneend of the coil spring is held by the protrusion holding portion 74 e,the position of the coil spring is unlikely to be displaced.

<Problems with Support Structure for Pair of First Output Rollers>

Generally, as exemplified in FIG. 15A, in the support structure 6 forthe driven roller 362 of the pair of first output rollers 36, each coilspring included in a corresponding pressing member 57 is disposed suchthat its end portion opposite to the abutting portion 74 d of acorresponding support 73 is pressed against part of a correspondingbearing 56.

The support structure 6 shown in FIG. 15A is a comparative supportstructure 60. Both ends of the coil spring serving as the pressingmember 57 are assumed to be parallel to each other and have asubstantially flat annular shape, unless otherwise specifically stated.Symbol L1 for a chain dashed line in FIG. 15A etc. represents a virtualstraight line (virtual line) connecting the rotation center 02 of thedriven roller 362 to the rotation center 01 of the driving roller 361.Symbol L2 for a chain dashed line represents the direction (the axialline) of the rotating shaft 52 of the driven roller 362.

In the comparative support structure 60, the coil spring serving as thepressing member 57 is disposed such that a central portion 57 a of anend of the coil spring that is pressed against part of the bearing 56substantially coincides with a position P1 at which the virtual line L1intersects a pressure receiving surface 56 e of the bearing 56 and is incontact with the pressure receiving surface 56 e. FIG. 15B shows aportion 57 b in which an end portion of the coil spring serving as thepressing member 57 is in contact with the pressure receiving surface 56e of the bearing 56 and also shows the state of the portion 57 b. Inthis support structure 60, the coil spring serving as the pressingmember 57 is attached on the assumption that the pressing force F of thecoil spring acts toward the rotation center 02 of the rotating shaft 52.

As shown in FIG. 15A, in this support structure 60, when the drivingroller 361 is rotated in a direction indicated by a chain double-dashedarrow at its operating timing, the driven roller 362 is driven to rotatein a rotation direction C indicated by a chain double-dashed arrow.

In this case, as shown in FIG. 15A, a rotational force (moment) Mr and arotational drag force (moment) Mb are generated and act on the bearing56. The rotational force Mr urges the bearing 56 to rotate in therotation direction C through the frictional force such as the slidingforce between the bearing 56 and the rotating shaft 52 of the drivenroller 362. The rotational drag force Mb is caused by the pressingmember 57 pressed against the bearing 56 and urges the bearing 56 torest against the rotational force Mr.

In fact, in the support structure 60, the coil springs serving as thepressing members 57 may have different pressing characteristics (mayhave their own unique pressing characteristics) depending on theattachment states of the coil springs, their individual differences,etc. In this case, as shown FIGS. 16A and 16B, each bearing 56 mayrotate about the rotating shaft 52 and come to rest while in contactwith part of the holding portion 74 a of the support 73 and inclinedwithin a movable space in the support 73.

FIG. 16A shows a state (J1) in which the bearing 56 slides within theholding portion 74 a of the support 73 in a direction opposite to therotation direction C of the driven roller 362 and is thereby inclinedand at rest. FIG. 16B shows a state (J2) in which the bearing 56 slideswithin the holding portion 74 a of the support 73 in the rotationdirection C of the driven roller 362 and is thereby inclined and atrest.

In this support structure 60, during rotation of the driven roller 362,the sliding friction between the bearing 56 and the rotating shaft 52may change instantaneously, and the rotational force Mr may increase ordecrease. Specifically, when a reduction in the sliding friction occurs,the rotational force Mr decreases. In this case, the rotational force Mrcan be substantially equal to the rotational drag force Mb (Mr≅Mb).

When these forces are substantially equal to each other, the bearing 56is unstable and can easily rotate about the rotating shaft 52 duringrotation of the driven roller 362. Therefore, the bearing 56 rotatesback and forth repeatedly between the above two states (J1 and J2).

Therefore, in the support structure 60, the bearing 56 repeatedlycollides with portions of the support 73, and this causes unwanted noiseand vibration. When a transport device 7 is formed using this supportstructure 60, unwanted noise and vibration are generated during transferof a recording paper sheet 9 by the transport device 7.

<Detailed Structure of Support Structure for Pair of First OutputRollers>

Accordingly, in exemplary embodiment 1, as the support structure 6 thatsupports the driven roller 362 of the pair of first output rollers 36, asupport structure 6A shown in FIGS. 4A and 5A is employed. In thesupport structure 6A, when the driven roller 362 serving as the rotarymember is not rotating, the bearing 56 and the pressing member 57 are incontact with each other while the bearing 56 is rotatable about therotating shaft 52.

The state in which the bearing 56 is rotatable is an unstable state.Specifically, for example, when the driven roller 362 is not rotating,the bearing 56 can easily rotate about the rotating shaft 52 in therotation direction C of the driven roller 362 (or its rotating shaft 52)and also in a direction opposite to the rotation direction C, as shownin FIG. 6A. Symbol L1 for a chain dashed line in FIG. 6A represents avirtual line connecting the rotation center 02 of the driven roller 362to the rotation center 01 of the driving roller 361, as does the virtualline L1 described above.

In the support structure 6A for the driven roller 362 in exemplaryembodiment 1, each pressing member 57 has a protrusion 81, and theprotrusion 81 is in contact with a corresponding bearing 56. When thedriven roller 362 is not rotating, the bearing 56 can rotate about therotating shaft 52.

Moreover, in the support structure 6A for the driven roller 362, duringrotation of the driven roller 362, the bearing 56 is held in a state inwhich it is rotated in the rotation direction C of the driven roller362, as shown in FIG. 6B.

The phrase “the bearing 56 is held in a state in which it is rotated inthe rotation direction C of the driven roller 362” means that, forexample, the bearing 56 rotated in the rotation direction C of thedriven roller 362 comes into contact with part of the holding portion 74a of the support 73 and is thereby inclined and at rest and the inclinedstate is maintained during the rotation of the driven roller 362, asshown in FIG. 6B. The phrase also encompasses the following case.

Specifically, during the rotation of the driven roller 362 in therotation direction C, the bearing 56 is brought to the inclined statedescribed above. Then the bearing 56 in the inclined state slightlyrotates continuously back and forth in the rotation direction C of thedriven roller 362 and its reverse rotation direction. In other words, inthis state, during the rotation of the driven roller 362 in the rotationdirection C, the bearing 56 is prevented from rotating in the reverserotation direction beyond the position at which the bearing 56 isunstable and rotatable when the driven roller 362 is not rotating (FIG.6A).

The protrusion 81 disposed in the pressing member 57 is formed as astructural member having a spherical surface portion that comes in tocontact with the pressure receiving surface 56 e of the pressurereceiving portion 56 d of the bearing 56.

As shown in FIG. 5B, the protrusion 81 formed as the sphericalsurface-shaped structural member is in point contact with the pressurereceiving surface 56 e of the pressure receiving portion 56 d of thebearing 56. This allows the bearing 56 to be easily rotatable when thedriven roller 362 is not rotating.

Symbol 81 a in FIG. 5B represents a portion of the protrusion 81 that isin contact with the bearing 56. The contact portion 81 a substantiallycorresponds to the apex of the spherical surface-shaped protrusion 81. Achain dashed line L2 in FIG. 5B indicates the direction (axial line) ofthe rotating shaft 52 of the driven roller 362 as described above.

In fact, the term “point contact” also encompasses the case in which theshape of the contact portion 81 a is a dot-like shape (a small circularshape) with a certain diameter (width) w1 on condition that shape of thecontact portion 81 a is maintained in the above-described rotatablestate as shown in FIG. 5B. The pressure receiving surface 56 e of thepressure receiving portion 56 d of the bearing 56 is a flat surface.However, the pressure receiving surface 56 e may be a curved surfacewith a small curvature so long as the point contact with the protrusion81 can be maintained.

As shown in FIGS. 7A and 7B, the pressing member 57 provided with theprotrusion 81 includes a coil spring 571 having a first end 571 a towhich a component 85 having the protrusion 81 is attached.

The component 85 having the protrusion 81 has an attachment recess 85 cinto which the first end 571 a of the coil spring 571 is fitted. Theprotrusion 81 may be integrated with the component 85, or the protrusion81 formed separately may be later integrated with the component 85.

The pressing member 57 provided with the protrusion 81 is disposed suchthat the protrusion 81 is pressed toward the rotation center 02 of therotating shaft 52 of the driven roller 362. Specifically, as shown inFIG. 6A, the pressing member 57 is disposed such that its pressing forceF acts toward the rotation center 02 of the rotating shaft 52.

In this case, the coil spring 571 serving as the pressing member 57 maybe attached such that a second end 571 b of the coil spring 571 isfitted onto and held by the protrusion holding portion 74 e (FIG. 4A)provided in the abutting portion 74 d of the support 73.

<Operational Advantages of Support Structure for Pair of First OutputRollers>

As shown in FIGS. 5A and 6A, in the support structure 6A supporting thedriven roller 362 of the pair of first output rollers, when the drivenroller 362 is not rotating (is in a non-rotating state), the bearing 56is in point contact with the protrusion 81 disposed in the pressingmember 57.

In the support structure 6A in this state, the bearing 56 is rotatableabout the rotating shaft 52 within the movable space in the holdingportion 74 a of the support 73. In this case, only the pressing force Fexerted by the pressing member 57 and directed to the rotation center 02of the rotating shaft 52 acts on the bearing 56. Therefore, the bearing56 is in an unstable state in which it can easily rotate about therotating shaft 52 in the rotation direction C of the driven roller 362and also in the reverse rotation direction.

As shown in FIG. 6B, in the support structure 6A, when the driven roller362 is rotating during, for example, transportation of a recording papersheet 9 (during rotation of the driven roller 362), the rotational forceMr in the rotation direction C of the driven roller 362 acts on thebearing 56, as described above for the comparative support structure 60.

Therefore, in the support structure 6A, the bearing 56 that is rotatablewhen the driven roller 362 is not rotating is maintained in a state inwhich the bearing 56 is rotated in the rotation direction C of thedriven roller 362 within the movable space in the holding portion 74 aof the support 73.

Specifically, as shown in FIG. 6B, the bearing 56 in this case isrotated in the rotation direction C of the driven roller 362 within themovable space in the holding portion 74 a of the support 73. Then part(a corner) of the bearing 56 comes into contact with part of the holdingportion 74 a, and the bearing 56 comes to rest, so that the bearing 56is slightly inclined.

Also in this support structure 6A, during rotation of the driven roller362, the sliding friction between the bearing 56 and the rotating shaft52 may change instantaneously, and the rotational force Mr may increaseor decrease, as described above for the comparative support structure60. Specifically, when a reduction in the sliding friction occurs, therotational force Mr decreases. In this case, the rotational force Mr andthe rotational drag force Mb may become substantially equal to eachother (Mr≅Mb).

However, in the support structure 6A, the protrusion 81 in the pressingmember 57 is in point contact with the bearing 56. Since the pressingmember 57 is disposed such that its pressing force F acts toward therotation center 02 of the rotating shaft 52, the vector of the loadgenerated by the protrusion 81 is directed toward the rotation center 02of the rotating shaft 52. Therefore, in the support structure 6A, therotational drag force (moment) Mb itself that is caused by the pressingmember 57 pressed against the bearing 56 and urges the bearing 56 torest against the rotational force Mr is unlikely to be generated.

Therefore, in the support structure 6A, the rotational drag force Mb isunlikely to increase to a level comparable to the rotational force Mr,and the relation between the rotational force Mr and the rotational dragforce Mb is easily maintained such that the rotational force Mr islarger than the rotational drag force Mb (Mr>Mb).

In this support structure 6A, during rotation of the driven roller 362(and the driving roller 361), the bearing 56 is easily maintained in astate in which it is rotated in the rotation direction C of the drivenroller 362 within the holding portion 74 a of the support 73. In thiscase, the bearing 56 is prevented from rotating in the reverse rotationdirection opposite to the rotation direction C beyond the position atwhich the bearing 56 is in the rotatable state when the driven roller362 is not rotating and from rotating back and forth repeatedly aroundthe above position.

Therefore, in the support structure 6A, generation of noise andvibration caused by repeated rotation of the bearing 56 within themovable space in the support 73 can be prevented or reduced, asdescribed above for the comparative support structure 60.

In the support structure 6A, the generation of noise and vibration thatoccurs during rotation of the driven roller 362 in the comparativesupport structure 60 is prevented or reduced. Therefore, in a transportdevice 7 produced using the support structures 6A, a recording papersheet 9 can be smoothly transported without generation of noise andvibration.

In the structural example shown in exemplary embodiment 1, theprotrusion 81 in point contact with the pressure receiving portion 56 dof the bearing 56 is a structural component having a spherical surfaceshape. However, this structural example is not a limitation. Forexample, the protrusion 81 may be a structural component in which theportion in contact with the pressure receiving portion 56 d of thebearing 56 has a cone shape or a pyramid shape.

In the support structure 6 in which the protrusion 81 in point contactwith the bearing 56 is used, even when the driven roller 362 is rotatedin the rotation direction C and the reverse rotation direction in aswitchable manner, the bearing 56 is rotated in the direction ofrotation of the driven roller 362 (the rotation direction C or thereverse rotation direction).

In the support structure 6A, even when the driven roller 362 is rotatedin the forward and reverse directions in a switchable manner, thegeneration of noise and vibration caused by repeated rotation of thebearing 56 as described above is prevented.

EXEMPLARY EMBODIMENT 2

FIGS. 8A and 8B show a support structure 6B for the driven roller 362 inexemplary embodiment 2.

The support structure 6B according to exemplary embodiment 2 has thesame structure as the support structure 6A according to exemplaryembodiment 1 except that the protrusion 81 is replaced with a protrusion82 having a different structure. Therefore, in the support structure 6B,the same components as the support structure 6A are denoted by the samesymbols in FIGS. 8A and 8B and subsequent figures, and their descriptionwill be omitted in principle.

As shown in FIGS. 8A and 8B, in the support structure 6B, the protrusiondisposed in the pressing member 57 is a protrusion 82 in line contactalong the axial line L2 of the rotating shaft 52 with the pressurereceiving surface 56 e of the pressure receiving portion 56 d of thebearing 56. Therefore, as shown in FIGS. 8A, 8B, and 9A, when the drivenroller 362 is not rotating, the bearing 56 is rotatable about therotating shaft 52.

Also in this support structure 6B, as in the support structure 6Aaccording to exemplary embodiment 1, during rotation of the drivenroller 362, the bearing 56 is held in a state in which it is rotated inthe rotation direction C of the driven roller 362, as shown in FIG. 9B.

The protrusion 82 is formed as a structural component in which itsportion coming into contact with the pressure receiving surface 56 e ofthe bearing 56 can be in line contact along the axial line L2 of therotating shaft 52. As shown in FIG. 10A, the protrusion 82 is formed as,for example, a horizontally extending triangular prism-shaped structuralcomponent having an edge line 82 a that comes into contact with thebearing 56.

As shown in FIG. 8B, the protrusion 82 having the portion capable ofline contact comes into line contact with the pressure receiving surface56 e of the pressure receiving portion 56 d of the bearing 56.

In this case, when the driven roller 362 is not rotating, the bearing 56can be easily brought to the above-described rotatable state. When theprotrusion 82 in line contact along the axial line L2 of the rotatingshaft 52 is used, the bearing 56 is further prevented from beinginclined accidentally in a direction intersecting the axial line L2, ascompared to the case when the protrusion 81 in point contact is used.Therefore, the posture of the bearing 56 in the direction of the axialline L2 is stabilized.

The term “line contact” encompasses the case in which the contactportion 82 a of the protrusion 82 has a continuous or discontinuousrectangular shape with a certain width w2 on condition that the bearing56 is maintained in the above-described rotatable state, as shown inFIG. 8B. In this case, the width w2 is shorter than the length k1 of thecontact portion 82 a along the axial line L2 of the rotating shaft 52(w2<k1).

The pressing member 57 provided with the protrusion 82 includes a coilspring 571 having an end to which a component 85 having the protrusion82 is attached (e.g., FIG. 8A), as is the pressing member 57 providedwith the protrusion 81 (FIGS. 7A and 7B).

<Operational Advantages of Support Structure for Pair of First OutputRollers>

As shown in FIGS. 8A, 8B, and 9A, in the support structure 6B supportingthe driven roller 362, when the driven roller 362 is not rotating, thebearing 56 is in line-contact with the protrusion 82 in the pressingmember 57.

In the support structure 6B in this case, as in the support structure6A, the bearing 56 is rotatable about the rotating shaft 52 within themovable space in the holding portion 74 a of the support 73. In thiscase, the bearing 56 is in an unstable state in which it can easilyrotate in the rotation direction C of the driven roller 362 and also inthe reverse rotation direction. However, the posture of the bearings 56along the axial line L2 of the rotating shaft 52 is in a stable state.

As shown in FIG. 9B, in the support structure 6B, when the driven roller362 is rotating, the rotational force Mr in the rotation direction C ofthe driven roller 362 acts on the bearing 56, and therefore the bearing56 is held in a state in which it is rotated in the rotation direction Cof the driven roller 362 within the movable space in the holding portion74 a of the support 73.

Specifically, as shown in FIG. 9B, the bearing 56 in this case isrotated in the rotation direction C of the driven roller 362 within themovable space in the holding portion 74 a of the support 73. Then part(a corner) of the bearing 56 comes into contact with part of the holdingportion 74 a, and the bearing 56 comes to rest, so that the bearing 56is slightly inclined.

In this the support structure 6B, as in the support structure 6A, duringrotation of the driven roller 362, the sliding friction between thebearing 56 and the rotating shaft 52 may change instantaneously, and therotational force Mr may increase or decrease. For example, therotational force Mr and the rotational drag force Mb may becomesubstantially equal to each other (Mr≅Mb).

However, in the support structure 6B, the protrusion 82 in the pressingmember 57 is in line contact with the bearing 56. Since the pressingmember 57 is disposed such that its pressing force F acts toward therotation center 02 of the rotating shaft 52, the vector of the loadgenerated by the protrusion 82 is directed toward the rotation center 02of the rotating shaft 52. Therefore, in the support structure 6B, as inthe support structure 6A, the rotational drag force Mb itself that iscaused by the pressing member 57 pressed against the bearing 56 andurges the bearing 56 to rest against the rotational force Mr is unlikelyto be generated.

Therefore, also in the support structure 6B, as in the support structure6A, the rotational drag force Mb is unlikely to increase to a levelcomparable to the rotational force Mr, and the relation between therotational force Mr and the rotational drag force Mb is easilymaintained such that the rotational force Mr is larger than therotational drag force Mb (Mr>Mb).

Also in this support structure 6B, during rotation of the driven roller362, the bearing 56 is easily maintained in a state in which it isrotated in the rotation direction C of the driven roller 362 within theholding portion 74 a of the support 73. In this case, the bearing 56 isprevented from rotating in the reverse rotation direction opposite tothe rotation direction C beyond the position at which the bearing 56 isin the rotatable state when the driven roller 362 is not rotating andfrom rotating back and forth repeatedly around the above position.

Therefore, also in this support structure 6B, as in the supportstructure 6A, generation of noise and vibration caused by repeatedrotation of the bearing 56 within the movable space in the support 73can be prevented or reduced.

In exemplary embodiment 2, the protrusion 82 in line contact may be, forexample, a structural body including a semicylindrical member having anapex portion (ridge line) 82 b extending substantially linearly in alengthwise direction, as shown in FIG. 10B. This structural body may bedisposed such that the apex portion 82 b comes into contact with thebearing 56.

In this case, the apex portion 82 b of the protrusion 82 is less worndue to contact with the bearing 56 than the protrusion 82 of thestructural body shown in FIG. 10A, and the bearing 56 can be maintainedin a desirable state for a long time.

EXEMPLARY EMBODIMENT 3

FIG. 11 shows a support structure 6C for the driven roller 362 inexemplary embodiment 3.

The support structure 6C according to exemplary embodiment 3 has thesame structure as the support structure 6A according to exemplaryembodiment 1 except that the protrusion 81 is disposed in the bearing56. Therefore, in the support structure 6C, the same components as thesupport structure 6A are denoted by the same symbols in FIGS. 11A and11B and subsequent figures, and their description will be omitted inprinciple.

In the support structure 6C, the protrusion disposed in the bearing 56is a protrusion 83 that comes into point contact with one end of a coilspring serving as the pressing member 57, as shown in FIGS. 11A and 11B.Therefore, as shown in FIGS. 11A, 11B, and 12A, when the driven roller362 is not rotating, the bearing 56 is rotatable about the rotatingshaft 52.

Also in this support structure 6C, as in the support structure 6Aaccording to exemplary embodiment 1, during rotation of the drivenroller 362, the bearing 56 is held in a state in which it is rotated inthe rotation direction C of the driven roller 362, as shown in FIG. 12B.

The protrusion 83 disposed in the bearing 56 is formed as a structuralcomponent in which its portion coming into contact with one end of thepressing member 57 has a spherical surface shape, as is the protrusion81 in the support structure 6A. In this case, the pressing member 57 isformed as, for example, a coil spring 571 to which a component 85 havinga flat surface serving as a portion 85 a to be in contact with theprotrusion 83 is attached to the one end.

As shown in FIG. 11B, the protrusion 83 formed as the sphericalsurface-shaped structural body comes into point contact with the one endof the coil spring 571 serving as the pressing member 57 (the flatportion 85 a of the component 85). In this manner, when the drivenroller 362 is not rotating, the bearing 56 can be easily brought to theabove-described rotatable state.

Symbol 83 a in FIG. 11B represents a portion of the protrusion 83 thatis in contact with the one end of the coil spring 571 serving as thepressing member 57. The contact portion 83 a substantially correspondsto the apex of the spherical surface-shaped protrusion 83.

In the support structure 6C, as in the support structure 6A, thepressing member 57 is disposed so as to be pressed toward the rotationcenter 02 of the rotating shaft 52 of the driven roller 362.Specifically, as shown in FIG. 12A, the pressing member 57 is disposedsuch that its pressing force F acts toward the rotation center 02 of therotating shaft 52.

<Operational Advantages of Support Structure for Pair of First OutputRollers>

As shown in FIGS. 11A, 11B, and 12A, in this support structure 6C, whenthe driven roller 362 is not rotating, the protrusion 83 disposed in thebearing 56 is in point contact with the one end of the pressing member57.

In the support structure 6C in this case, substantially as in thesupport structure 6A, the bearing 56 is rotatable about the rotatingshaft 52 within the movable space in the holding portion 74 a of thesupport 73. In this case, the bearing 56 is in an unstable state inwhich it can easily rotate in the rotation direction C of the drivenroller 362 and also in the reverse rotation direction. However, theposture of the bearing 56 along the axial line L2 of the rotating shaft52 is in a stable state.

As shown in FIG. 12B, in the support structure 6C, when the drivenroller 362 is rotating, the rotational force Mr in the rotationdirection C of the driven roller 362 acts on the bearing 56. Therefore,the bearings 56 is held in a state in which it is rotatable in therotation direction C of the driven roller 362 within the movable spacein the holding portion 74 a of the support 73.

Specifically, as shown in FIG. 12B, the bearing 56 in this case isrotated in the rotation direction C of the driven roller 362 within themovable space in the holding portion 74 a of the support 73. Then part(a corner) of the bearing 56 comes into contact with part of the holdingportion 74 a, and the bearing 56 comes to rest, so that the bearing 56is slightly inclined.

In the support structure 6C, as in the support structure 6A etc., duringrotation of the driven roller 362, the sliding friction between thebearing 56 and the rotating shaft 52 may change instantaneously, and therotational force Mr may increase or decrease. Therefore, for example,the rotational force Mr and the rotational drag force Mb may becomesubstantially equal to each other (Mr≅Mb).

However, in this support structure 6C, the protrusion 83 in the bearing56 is in point contact with the pressing member 57. Since the pressingmember 57 is disposed such that its pressing force F acts toward therotation center 02 of the rotating shaft 52, the vector of the loadgenerated by the protrusion 83 is directed toward the rotation center 02of the rotating shaft 52. Therefore, in the support structure 6C, therotational drag force Mb itself that is caused by the pressing member 57pressed against the bearing 56 and acts against the rotational force Mris unlikely to be generated.

Therefore, also in the support structure 6C, because of substantiallythe same reason as in the support structure 6A etc., the rotational dragforce Mb is unlikely to increase to a level comparable to the rotationalforce Mr, and the relation between the rotational force Mr and therotational drag force Mb is easily maintained such that the rotationalforce Mr is larger than the rotational drag force Mb (Mr>Mb).

Also in this support structure 6C, during rotation of the driven roller362, the bearing 56 is easily maintained in a state in which it isrotated in the rotation direction C of the driven roller 362 within theholding portion 74 a of the support 73. In this case, the bearing 56 isprevented from rotating in the reverse rotation direction opposite tothe rotation direction C beyond the position at which the bearing 56 isin the rotatable state when the driven roller 362 is not rotating andfrom rotating back and forth repeatedly around the above position.

Therefore, also in the support structure 6C, substantially as in thesupport structure 6A, generation of noise and vibration caused byrepeated rotation of the bearing 56 within the movable space in thesupport 73 can be prevented or reduced.

In exemplary embodiment 3, the protrusion 83 in point contact may be,for example, a different structural member such as that described inexemplary embodiment 1.

In exemplary embodiment 3, the protrusion 82 in line contact asexemplified in exemplary embodiment 2 may be used instead of theprotrusion 83 in point contact.

EXEMPLARY EMBODIMENT 4

FIG. 13 shows a support structure 6D for a charging roller 220 inexemplary embodiment 4 and the charging device 22 using the supportstructure 6D.

This support structure 6D supports the charging roller 220 in thecharging device 22 of the image forming unit 2. For example, the supportstructure 6A according to exemplary embodiment 1 (FIGS. 4A, 4B, 5A, 5B,etc.) is used as the support structure 6D.

The charging roller 220 is a rotary member 5C including, for example: arotating shaft 221 to which a charging voltage is supplied; and a rollerbody 222 disposed on the rotating shaft 221 and having a multilayerstructure including an elastic layer, a surface layer, etc. The chargingroller 220 is in contact with the circumferential surface of thephotoreceptor drum 21 rotating in the direction of arrow A and is drivento rotate by the photoreceptor drum 21 in a direction indicated by chaindouble-dashed arrow D, and the circumferential surface of thephotoreceptor drum 21 is thereby charged.

A chain dashed line L3 in FIG. 13 etc. represents a virtual straightline (virtual line) connecting the rotation center 03 of thephotoreceptor drum 21 to the rotation center 04 of the charging roller220. A double-pointed arrow denoted by symbols E3 and E4 indicatesmoving directions when the support 73 movably supports the bearing 56 ofthe charging roller 220.

As shown in FIG. 13, in the support structure 6D supporting the chargingroller 220, substantially as in the support structure 6A according toexemplary embodiment 1, the protrusion 81 disposed in the pressingmember 57 is in point contact with the pressure receiving surface 56 eof the pressure receiving portion 56 d of the bearing 56 (see, forexample, FIG. 6B). In this case, as shown in FIG. 14A, when the chargingroller 220 is not rotating, the bearing 56 is rotatable about therotating shaft 221.

As shown in FIG. 14B, also in this support structure 6D, substantiallyas in the support structure 6A according to exemplary embodiment 1, whenthe charging roller 220 is rotating, the bearing 56 is maintained in astate in which it is rotated in the rotation direction D of the chargingroller 220.

<Operational Advantages of Support Structure for Charging Roller>

As shown in FIGS. 13 and 14A, in the support structure 6D for thecharging roller 220, when the charging roller 220 is not rotating, thebearing 56 is in point contact with the protrusion 81 disposed in thepressing member 57.

In the support structure 6D in this case, as in the support structure6A, the bearing 56 is rotatable about the rotating shaft 221 within themovable space in the holding portion 74 a of the support 73.

As shown in FIG. 14B, in the support structure 6D, when the chargingroller 220 is rotating, the rotational force Mr in the rotationdirection D of the charging roller 220 acts on the bearing 56.Therefore, the bearing 56 is held in a state in which it is rotatable inthe rotation direction D within the movable space in the holding portion74 a of the support 73.

Specifically, as shown in FIG. 14B, the bearing 56 in this case isrotated in the rotation direction D of the charging roller 220 withinthe movable space in the holding portion 74 a of the support 73. Thenpart (a corner) of the bearing 56 comes into contact with part of theholding portion 74 a, and the bearing 56 comes to rest, so that thebearing 56 is slightly inclined.

Also in the support structure 6D, as in the support structure 6A, duringrotation of the charging roller 220, the sliding friction between thebearing 56 and the rotating shaft 221 may change instantaneously, andthe rotational force Mr may increase or decrease. For example, therotational force Mr and the rotational drag force Mb may becomesubstantially equal to each other (Mr≅Mb).

However, in the support structure 6D, because of the same reason as inthe support structure 6A, the rotational drag force Mb is unlikely toincrease to a level comparable to the rotational force Mr, and therelation between the rotational force Mr and the rotational drag forceMb is easily maintained such that the rotational force Mr is larger thanthe rotational drag force Mb (Mr>Mb).

Also in this support structure 6D, during rotation of the chargingroller 220, the bearing 56 is easily maintained in a state in which itis rotated in the rotation direction D of the charging roller 220 withinthe holding portion 74 a of the support 73. In this case, the bearing 56is prevented from rotating in the reverse rotation direction opposite tothe rotation direction C beyond the position at which the bearing 56 isin the rotatable state when the charging roller 220 is not rotating andfrom rotating back and forth repeatedly around the above position.

Therefore, also in the support structure 6D, as in the support structure6A, generation of noise and vibration caused by repeated rotation of thebearing 56 within the movable space in the support 73 can be preventedor reduced.

In the support structure 6D, the generation of noise and vibrationduring rotation of the charging roller 220 is prevented or reduced.Therefore, in the charging device 22 formed using the support structure6D, charging can be performed desirably without generation of noise andvibration.

OTHER EXEMPLARY EMBODIMENTS

In the structural examples shown in exemplary embodiments 1 to 3, one ofthe support structures 6A to 6C is used as the structure for supportingthe driven roller 362 (the rotary member 5B) of the pair of first outputrollers 36. However, any of them may be used as a structure forsupporting the driving roller 361 (the rotary member 5A) of the pair offirst output rollers 36.

In the pair of first output rollers 36, the driving roller 361 may bereplaced with an elastic roller having the function of correcting curlof a recording paper sheet 9. The elastic roller is, for example, acontinuous single roller such as the driven roller 362, and an elasticbody is used as its roller body.

Each of the support structures 6A to 6C exemplified in exemplaryembodiments 1 to 3 can be used for a transport device including a pairof transport rollers (rotary members) that are in pressure contact witheach other and are rotated and transport a recording paper sheet 9 heldtherebetween. Specifically, each of the support structures 6A to 6C canbe used as a support structure for at least one of the pair of transportrollers.

Each of the support structure 6A to 6C exemplified in exemplaryembodiments 1 to 3 can be used as the support structure 6D for thecharging roller 220 in the charging device 22 of the image forming unit2 exemplified in exemplary embodiment 4, but this is not a limitation.Each of the support structures 6A to 6C may be used as the supportstructure for a different rotary member. Examples of such a rotarymember include a transfer roller and fixing roller.

Each of the support structures 6A to 6C may be used as the supportstructure for a pressing roller pressed against a portion of an endlessbelt that is not supported by a support roller. In this case, a rotarymember in contact with the pressing roller is a portion of the rotatingbelt that is not supported by the support roller.

Moreover, an image forming apparatus including the rotary member usingone of the support structures 6A to 6D and the transport device 7 or thecharging device 22 is not limited to the apparatus forming a monochromeimage using a single-color toner as exemplified in exemplary embodiments1 to 4. Image forming apparatuses of different types may be used.

Examples of the image forming apparatuses of different types include: animage forming apparatus that forms a multicolor image using acombination of plural color toners; and an image forming apparatus thatforms an image by jetting ink droplets.

The rotary member and the transport device 7 that use any of the supportstructures 6A to 6C may be a rotary member and a transport device of anapparatus other than the image forming apparatus.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. A rotary member support structure comprising: arotary member including a shaft; a bearing that rotatably supports theshaft of the rotary member; a pressing member that presses the bearingin one direction; and a support that supports the bearing such that thebearing is movable in a pressing direction of the pressing member,wherein, when the rotary member is not rotating, the bearing and thepressing member are in contact with each other such that the bearing isrotatable about the shaft.
 2. A rotary member support structurecomprising: a rotary member including a shaft; a bearing that rotatablysupports the shaft of the rotary member; a pressing member that pressesthe bearing in one direction; and a support that supports the bearingsuch that the bearing is movable in a pressing direction of the pressingmember, wherein a first one of the bearing and the pressing member has aprotrusion, and a second one of the bearing and the pressing member isin contact with the protrusion, and wherein, when the rotary member isnot rotating, the bearing is rotatable about the shaft.
 3. The rotarymember support structure according to claim 1, wherein, during rotationof the rotary member, the bearing is maintained in a state in which thebearing is rotatable in a rotation direction of the rotary member. 4.The rotary member support structure according to claim 2, wherein,during rotation of the rotary member, the bearing is maintained in astate in which the bearing is rotatable in a rotation direction of therotary member.
 5. The rotary member support structure according to claim1, wherein the pressing member is disposed so as to press the bearingtoward the rotation center of the shaft of the rotary member.
 6. Therotary member support structure according to claim 2, wherein thepressing member is disposed so as to press the bearing toward therotation center of the shaft of the rotary member.
 7. The rotary membersupport structure according to claim 1, wherein the bearing and thepressing member are in point contact with each other or in line contactwith each other along an axial line of the shaft.
 8. The rotary membersupport structure according to claim 2, wherein the protrusion and thesecond one of the bearing and the pressing member are in point contactwith each other or in line contact with each other along an axial lineof the shaft.
 9. The rotary member support structure according to claim2, wherein the protrusion is disposed in the pressing member.
 10. Therotary member support structure according to claim 9, wherein thepressing member is a coil spring in which a component having theprotrusion is attached to one end thereof.
 11. A transport devicecomprising: a pair of transport rotary members that transport atransportation object held therebetween; and the rotary member supportstructure according to claim 1, the rotary member support structuresupporting at least one of the pair of transport rotary members.
 12. Acharging device comprising: a charging rotary member; and the rotarymember support structure according to claim 1, the rotary member supportstructure supporting the charging rotary member.
 13. An image formingapparatus comprising the rotary member support structure according toclaim
 1. 14. An image forming apparatus comprising the transport deviceaccording to claim
 11. 15. An image forming apparatus comprising thecharging device according to claim 12.